Protective eyewear or eyeglasses (e.g., sunglasses) having tinted lenses are commonly used in connection with various sports and other activities to protect the participant's eyes. Eye protection is especially needed when the sport or other activity involves unshielded high-speed travel wherein the eyes are susceptible to being impacted by small particles of foreign matter at velocities which equal the rate of travel. Examples of such sporting activities wherein eye protection is recommended include downhill skiing, snowmobiling, cycling, jet skiing and motorcycle racing to keep snow, water, dust, insects, small rocks, etc., out of the participant's eyes.
When protective eyeglasses are used in relation to the above-identified activities, a well-known problem that is often encountered is the fogging or misting, i.e., the build-up of condensation, on the inside surfaces of the lenses. The fogging problem is particularly severe when the wearer is warm and/or perspiring, with the outdoor environment being cool and/or damp. As will be recognized, the fogging of the lenses of the eyeglasses interferes with the wearers vision, and thus presents a potentially hazardous condition.
The problem of lens fogging has been recognized in the prior art wherein several solutions have been proposed to prevent such fogging from occurring. More particularly, in the prior art there are thermal lenses which each consist of a single lens of increased thickness. The increased thickness of the thermal lenses is operative to isolate the outside surfaces of the lenses exposed to the cooler air from the inside surfaces of the lenses which are exposed to the warmer air. Also known in the prior art are double glass lenses, each of which consists of a pair of lens halves separated by an intermediate air-filled space or void. The double glass lenses are also operative to facilitate the isolation of the outermost and innermost surfaces of the lenses from each other. However, the prior art thermal and double glass lenses significantly add to the bulk and weight of the eyeglasses in which they are used, and thus are uncomfortable to wear and not desirable for use in relation to sports activities.
There is also known in the prior art various coatings which are applied to the inside surfaces of the lenses for purposes of immediately condensing or absorbing any mist or fog which accumulates on the inside surfaces. However, such coatings are only effective for an extremely limited duration of time, with the inside surfaces of the glasses periodically needing to be dried in some manner.
It has been recognized in the prior art that the most effective manner of preventing the fogging or misting of the lenses of eyeglasses is to improve air circulation behind the lenses thereof, i.e., exhausting the warm humid air and replacing it with cool drier air. To facilitate such air exchange, there has been developed in the prior art eyeglasses incorporating miniature fans powered by portable batteries carried by the user. However, the eyewear incorporating these miniature fans is extremely complex and costly to manufacture, and is also bulky and of high weight. There has also been developed in the prior art eyeglasses which include ventilation ports disposed within various locations about the periphery of the frame so as to surround the lenses thereof. However, in these prior art eyeglasses, because of the manner in which the ventilation ports are configured and/or oriented, they typically provide either too little or too great a rate of air flow therethrough. Insufficient air flow through the ventilation ports makes the inclusion of the ventilation ports in the frame largely ineffective for purposes of preventing the fogging of the lenses. At the other extreme, too great a rate of air flow through the ventilation ports results in a pressure build-up or in uncomfortably high "winds" across the wearer's eyes. Moreover, the ventilation ports included in the prior art eyeglasses are often sized and configured in a manner wherein foreign manner, e.g., dust, can pass therethrough into the wearer's eyes.
In view of the foregoing, there exists a need for eyeglasses which can safely and adequately protect a wearer's eyes and are resistant to fogging. Such eyeglasses should be simple in construction and thus inexpensive to manufacture, and should further be lightweight so as not to unduly interfere with the wearer's participation in a certain sports activity.